Air intake control apparatus for gas turbine power plants



w. G; ovENs 2,570,847 AIR INTAKE CONTROL APPARATUS Oct. 9, 1951 FOR GAS TURBINE POWER PLANTS 2 Sheets-Sheet l Filed Jan. 29, 1949 INVENTOR. AWILLIAM E DVENE.

Oct 9, 1951 w. G. ovENs 2,570,847

AIR INTAKE CONTROL APPARATUS FOR GAS TURBINE POWER PLANTS Filed Jan. 29, 1949 2 Sheets-Sheet 2 i ilE-7 1 l j/wlLLlAh/NIQNEL A BY ATTEIRNEY Patented ct. 9, 1951 siasi? AIR INTAKE CONTROL APPARATUS FOR GAS TURBINE PQWER. PLANTS William G. Ovens, Ramsey, N. J., assigner to Wright Aeronautical Corporation, a corpora` tion of New York ApplicationJanuary 29, 1949, Serial No. 73,613 6 Claims. (61.60-39.29)-

1 Y This invention relates to 'gas turbine' engines for aircraft and is particularly directed to means for limiting the' pressure within the turbine combustion chamber and/or for limiting the turbine power output.

Gas turbine aircraft engines generally comprise a forwardly directed intake duct and a compressor drivably connected to the turbine, vsaid compressor discharging its compressed air into the turbine combustion chamber. When such a gas turbine Yaircraft engine is operated at or near the maximum available power at sea level in an atmosphere of low temperature and/or at high aircraft air speeds, the vram pressure of the air entering the intake duct of the compressor is such that, with the pressure increase produced by the compressor, the pressure differential across the walls of the turbine combustion chamber becomes quite high. It usually is not economically feasible or desirable to make the combustion chamber of an aircraft gas turbine power plant su'ciently strong to withstand these high or excessive internal pressures. An object of the invention comprises the provision of a novel arrangement for preventing excessive pressure differentials across the walls of the combustion chamber. In accordance with the present invention means are provided for automatically decreasing the ram pressure of the air intake of the turbine compressorrwhenever Vthe turbine combustion chamber pressure 'exceeds a predeter mined value. l

If the gas turbine power plant includes an aircraft propeller drivably connected to the turbine rotor through a speed reduction gear, the torque transmitted by said reduction gear may exceed that for which said reduction gear is designed when the power plant is operated at the maximum available power at sea level in an atmosphere of low temperature and/or at high aircraft air speeds. Here again it usually is not economically feasible or desirable to design said reduction gear for such high torques. Accordingly the aforementioned means for reducing the ram pressure to the turbine compressor can also be arranged to prevent said reduction gear torque from exceeding a predetermined value. Where the control of the maximum pressure differential across the walls of the turbine combustion cham- Y ber is used to limit the propeller reduction gear torque, said control may be biased vso as to de'y put of a turbine increases with decrease in said temperature.

Other objects of the inventionwill become apparent upon reading the annexed detailed description in connection with the drawing in which: A

Figure 1 is a diagrammatic View of a lgas turbine aircraft power plant embodying the jinvention;

Figure 2 is a partial perspective view of the air obstructing means incorporated in the power plant of Figure 1 with said means moved to its air obstructing position;

Figure 3 is a sectional View taken along line 3-3 of Figures l and 2 with the air obstructing fingers in their retracted positions;

Figure 4 is a diagrammatic view of the control mechanism embodied in Figure 1;

Figure 5 illustrates a modification of the air obstructing means of Figures 1. and 2.v

Figure 6 illustrates a modification of the control mechanism of Figure 4; and

Figure '7 illustrates a further modification of the control mechanism of Figure 4.

Referring to the drawing, a gas turbine power plant IU comprises a compressor I2 having a forwardly directed annular air intake duct I4, said compressor supplying compressed air into a c-ombustion chamber I6. Fuel nozzles I8 supply fuel into the combustion chamber I6 for combustion with said air. The combustion gases discharge from the chamber I6 against the blades 2li of a turbine 22, said turbine being drivably connected to the compressor I2. From the turbine blades 2l, the combustion gases discharge rearwardly therefrom through an exhaust duct or nozzle 24. The power plant is disposed within an outer casing or cowl 2S. The gas turbine power plant so far described is quite conventional.

An annular ring 28 forms the outer wall of the forward end of the intake duct I4, said ring `of said segment. Each segment 3U is also provided with extensions or fingers 3S which are arranged to be received within the recesses 30, as best seen in Figure 3. The arrangement is such housings 44 and 44d respectively, of these servo mechanisms are illustrated in ljigu're 4. The liou'sirig'M'hasV a'bore'46 within 3 that when the ngers 36 are received within the recesses 30, the segments 32 with their fingers 35 and the ring 28 form a smooth annular outer wall for a forward portion of the duct I4.

Each segment 32 is also provided with an arm 38 extending outwardly therefrom and a rod 40 is secured toeach of said'arms for swinging the associated segment 32 about its hinge axis so as to move or extend its fingers 36 across the duct I4, for example to the position illustrated in Figure 2. When the ngers'36 Aare extended, they obstruct the air flow into the duct"l4 and spoil the ram pressure of the air attheentrance to the compressor I2, the magnitude of said action depending on the degree to which said ngers are extended. p

As illustrated in Figure 4, "ach"ro'd"46is 'connected by a piston rod to a fluid motorfpiston, one of said piston rods and its piston being desighated by reference characters 4I and 42 respectively andthe other'piston rods 'and their pistons by reference characters 4 I a and 42a. Thepistons 42a are arranged to rfollow the/motion' ofthe piston 4 2 so that the pistof'n'42n maybe termed themaster pistonv and the 'pistons v42cL'theslaw"/e pSOnS-,- s

Ihe pi stons '4 2 and'j42o'-cmpr'se'the 'power members of Vservomechanismsdisposed lwithin The details which the master piston 42y is slidable. The housingr 44 also has a secondu bore vfithin= which a valve sleeve 5fis`slidable. A'val've' 52 is slidable within the sleeve55saidlvalve having an `annular grqove 54 intermediate its endsV and having "a rod 56 extendihg through one'end of the Ysleeve 56 to connect the valve to a 1ever58 at a point '66 intermediatethelever ends. One end"62 of the .lever 58 is pivqtal'lyfconectedfto the'pis'ton' rod 4l and its`otherv end is pivotallybonnected to motion ofv thefpiston' 42 r'is accompanied by" a proportional motionht the valve' 52.

The ends rof the sleeve'5 are closed and 'one end'of the bore'f48wwithin whichsaid sleeve is sudame' is 'subjected to thepressure withinjthe combustion chamber- I 6 through ay 'conduit '66. The other end of saidbore 48`is subjected to the pressure Wthinlth'aeelil Stab@ 'S8 bewn the combustion chamberand the 'cowl 26 through a passage '16. Af compression spring i2 is also d iSpQSsd Witt-11.1. Seid letteren@ Qf' the' 'bote' for urgingihesleeve egaifist the 'fib'in pressure.` Ihespr ngA 'l2 seats against t'p'lig'fill which isscrewed'into' the4 bore"`43 for initial adjustment 'against 'sa'id" spring.

A suitable uid'un'd'erprssure is 'siipp'lied'to the kannular groove 5 4 through a` conduit 76;' a

through e radial hle' 84. .in .Said Sleeve@ d' a linear-groove 86 inthe housing 4 4. Themr'ight to the drain passage@ `throughalfra'dial' liole'r',

. in said snssusessosvseinigermasing 44'. Ihe arrangement is such thatbo'th'nds "'94 and' '96. Thehole'64 communicates'with'the adjacent end of the piston bore 46 through a holes 9 4 'and"'96. "sle'e've 56 'results in'a correspondingi'm'ovement ofthe piston 42' and the valve `52.

4 linear groove 98 and a passage IBO and the hole 66 communicates with the other end of said piston bore through a linear groove |62 and a passage |04.

With the above described construction, when the valve 52 closes the holes 94 wand 66, both ends of the piston bore am'. closed l:so that the piston 42 is in a stable or xed'position. When j; the pressure within the combustion chamber I6 Vincreases to an extent sufficient to move the Ysleeyef 5ll tothe'right against the spring l2, the vh`olef94 is placed in communication with the annular groove 54 and the supply conduit 'I5 whereuponh fluid under pressure is admitted from the'fa-nnulargroove 54 through the hole 94 and Vpassage i to the left end of the piston bore 46. 3At thesametime the hole 96 is placed in communication with the continuously vented right end of the bore-in the sleeve 56 thereby venting the right end of the pistonv bore 46 through the passage les-ssahele-sa *Triassic pressure 'differential acting onthe "piston 42 moves 'said piston""to the right'l'tof4v extend tlie associated fingers't until; through vthe le ver'"58, the valve 52 is moved to the righteajsulc'int amount to follow upfthemov'ement of"the" `s le eve 56, that is until`the' 'valve A52 again' closes; both In this wa'y` movementof "the trol valves comprises'a slave unit whichissimil'ar 'ciated'valve"52. LYAccordingly no fui-ther description oftheA l'operation"ofeach `s1ave'unit*isf considered necessary.

In order to contratas-slave pistons again-1e 'master piston 42 "is: "connected vto 'ai ring' "H 8"-di'sposed and rotatable about the duct 'I4 in theannular space 68, a development of vsaid ring being 'illustrated inFi'giure 4. `"For this'latter'piirpose,

necte'd 'tothe' ring III)` for'limp'art'ing Ya""ro"ta ry motion to said ring proportional tothe motion "of V"the piston 42. l Instead ofbe'ing controlld'- by the pressure 'differential across tlfiewallsi offf'the each slave pistorr"`42a, are connected tofthefiring I I 6- byya bell crank lev'er -I'l 4 'pi-votally' mounted on'ftheir respective housings i44a. Accordingly,

v'since the slave pistons 42o` are controlled Aby their 'respective valve'sleevesSia and since sa'id'valve Lsleeves' 56m are controlledby-'the master-piston 4?,A the 'slave pistons *42a are controlled by said master piston. Y The lengths of-thearmsofthe bell crank lever |I4 are such that the rati o of the magnitude of the motion of each sleevea -'to that of the master piston 42"is equal v to` the `eifect'a movement'of the master' 'piston""42,; said ratio of the magnitude of"` the motion 'ofthe valve 52 to that of said "masterV piston. `With this valrrangeme'nt when 'the 'sleeve 56"'ino'ves 'to 'master piston, through the ring' Inland-'bell "Crank levers H4, produces -a motion ofA Vauch Vsleeve 50a equaltosaidmotionof vthe-sleeve 56. Therefore since the sleeves 50a and their valves 52a control the slave pistons 42a just as the sleeve 50 and valve 52 control the master piston 42, the movements of the slave pistons 42a follow and are equal to the movements of the master piston 42. y

When the pressure differential between the combustion chamber I6 and the annular space 68 is below a predetermined value, the master valve sleeve 50 is at the extreme left end of its travel so that the master piston 42 and valve 52 are also at the extreme left end of their travel. In addition since the master piston 42 is connected to the valve sleeves 50a of the slave pistons 42a, each sleeve 50a and its associated valve 52a and slave piston 42a are also at the extreme left ends of their travel. Accordingly all the fingers 36 are then completely retracted. If the pressure differential across the walls of the combustion chamber increases above this predetermined value, the sleeve 50 is moved to the right against this pressure differential and the master piston 42 and the slave pistons 42a all move to the right to extend the fingers 36 across the duct I4, the degree of which said fingers are extended depending on the extent to which the valve sleeve 5I) has been moved by the pressure differential across the walls of the combustion chamber. Thus the fingers 36 are normally completely retracted, said fingers only being extended when the pressure differential across the walls of the combustion chamber exceeds a pre-f determined value and then the fingers are extended only to a degree depending on the amount said pressure differential exceeds said predetermined value. When the fingers 36 are extended they obstruct the air fiow into the duct H4 and spoil the ram pressure at the entrance to the compressor I2 thereby effecting a reduction in the turbine combustion chamber pressure. In this way the fingers 36 automatically operate to prevent excessive combustion chamber pressures.

As illustrated, the fingers 36 are controlled by the Apressure differential between the pressure within the combustion chamber I6 and that within the annular space 68. Obviously however, said control may be responsive to some equivalent pressure differential, as for example to the pressure differential between the combustion chamber pressure and the pressure of the surrounding atmosphere or to the pressure differential between the combustion chamber pressure and the pressure in the exhaust nozzle or duct 24. l

The motor and control means orbperating the air obstructing fingers 36 has been described in considerable detail in order to disclose an operative structure. Obviously, however, the invention is not limited to the specific structure described. Thus any motor and control means which would operate to extend the fingers 36 to a degree determined by the extent to which the combustion pressure exceeds a predetermined value could be substituted for the motor and control means disclosed. For example an electric motor system could obviously be substituted for the fluid system disclosed. Furthermore where a variable pressure is used tocontrol the position of a member, the pressure itselfv may furnish the power for moving said member or a servo-valve mechanism may be provided wherein said pressure only controls the position of the servo-valve which in turn controls the application of another pressure to said member. Accordingly, it is obvious that instead of the servo-mechanism illustrated, the coinbustion chamber pressure itself could act against and furnishrthe power for moving the piston 42 and for moving the pistons 42a under the control of the piston 42. In addition the air obstrueting fingers 36 need not be as disclosed but any means movable across the air intake duct |4 could be used, as for example the structure schematically illustratedV in Figure 5. In fact it is obvious that the air obstructing means need not be in the form of fingers but may comprise any structure which can be moved into and out of a position for obstructing air flow into the duct I4.

In Figure 5 a group of air obstructing fingers |20 are supported by a link mechanism comprising a pair of links |22 and |24 having fixed pivots |26 and |28 respectively, a plurality of said groups of fingers |20 being circumferentially spaced about the intake duct I4. Each link |22 is integral with an arm |30 to form a bell crank lever, said arm being connected to a rod Y|32 which may be operated by the mechanism similar to that disclosed for operating the piston rods 40 of Figures 1 to 4. In Figure 5 the full lines indicate the retracted positions of the fingers |20 while the dashed lines indicate their fully extended positions. With the arrangement of Figures l to 4 the air flowing through the duct I4 opposes extension of the fingers 36 whereas with the arrangement of Figure 5 said air flow, to a small extent.

f helps said extension. Accordingly it is obvious that the air obstructing kfingers may be mounted so that the air flowing through the duct |4 has little or no effecten extension and/or retraction of said fingers, or said air flow assists or resists extension and/or retraction of said fingers. For example in Figure 5 whether the air flow assists or resists extension of the fingers |20 depends on the relative lengths cf the links |22 and |24.

As illustrated the gas* turbine power plant is provided with a conventional aircraft propeller |34 so that at least some or all of the thrust is produced by said propeller. Such a power plant is termed a turbo-prop engine; Obviously, however, the invention also? can be used in` a gas turbine ypower plant having no aircraft propeller and in which all the thrust is produced by the jet propulsive effect of the exhaust gases, that is in a turbo-jet engine.

As is conventional, the aircraft propeller |34 is driven by the turbine through a reduction gear not shown but disposed within the space surrounded by the duct |4. Since the air obstructing fingers 36 and |20 automatically operate to limit the combustion chamber pressure said fingers alsoV limit the maximum available turbine power output thereby limiting the power which can be transmitted through the propeller reduction gear. Accordingly the air obstructing fingers can be provided not only for preventing excessive combustion chamber pressures but also for preventing excessive loads on the propeller reduction gear.

The maximum available power output of a gas turbine power plant increases with decrease in the temperature of the air entering the duct I4. Accordingly where the air obstructing fingers are used to limit the maximum load on the propeller reduction gear, the control system may be biased so as to effect extension of said fingers at lower combustion chamber pressures in response to a decrease in the temperature of the surrounding air. Such a modification is schematically illustrated in Figure 6 which is identical to the sysspring? 72. ff'the spring l2 a'smaller pressurediiferenti'al "across the walls of the combustion"chamberwill beeffective to move the valve sleeve 5`-Yto=`extend `the air obstructing ngers'SB. Y

tending from a cam lill. the compression of the spring'li sothataninv"tem ofi-Figures'l toni1 except*tlielplughlI hasbeen lreplaced 'by' afplug 4Hit! 'which is Yslida'ble within the bore "G48, :its position vbeing*controlled byf--a |44 and is provided withan -arm eld'extending therefrom. TheY outer'send of Y the-Sarno '|116 Nis pivotallyconnec'ted to -af'bellows yHi8 the'rinterior f of f'which 'communicates with a bulb'ffth'rough tube-*|52 `contain'a huid-:which v'expands i with increaseY in itemperatureand -thebulb vll is exv posed to YVthe'--'temperatu-reIofthe airl enteringor 'fin the ductL f4.

The arrangement iss-such that as the temperature of the air entering -`thefduct |'4 idecreases below a predetermined valuathey bellows |48 contracts thereby rotating the cam |42 clockwise-to'decreasethe compression inthe With a decrease in the compression *Instead of using the temperatureof 'the lair entering the duct I4 to control the spring T2, as in Figure 6, a pressure varying with the torque 'or power'output of the propeller reduction gear could be used. Such a pressure is generally available on aircraft engines,` for `exa'mizzle by -means of a torquemeter'such as disclosed in'PatentNo.

""2,28'9,285to R. Chilton. This modication is i.

:illustrated in Figure' in-which a piston IBfJ-is :urged to the right with a force proportional to thetorque'transmittedby the propeller reduction gear drive. Movement of the piston by this torque proportional force is opposed bya fluid pressure supplied by a pump M52, the piston being movable to control a vent |54 so that crease in said torque above a predeterminedk value results in a decrease insaidspring compression.

If the primary purpose of the air obstructing lingers is toy limit the power transmitted by the .propeller reduction gear, then the air obstructing iingers could be contiolledby-a pressure'differential proportional to thetordue transmitted by said reduction gear instead of b`y the-pressure differential across the'walls of the combustion chamber. For example in'liguresY l toll,v instead of 'connecting the conduit to the combustion chamber it could be 'connectedto a pressure. proportional to said torque for example'ito the output pressure of the pump 62 of'FigureG.

While I have described my'invcntion in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after under- Astandingmyinvention, that various changes and modications mayibe made v.therein-witliout departing from the spirit or Vscope thereof. I aim in the appended claims to Coverall such. modications.

I claim as my invention:

1 1. In. combination withan aircraft gas turbine power plant..having a combustionV chamber,` an annular forwardly directed air intake duct havving an annular inlet opening disposed adjacentT to-the forward'end o'f-sa'd power '-plant, an -ai'r "compressor for supplying-said A combustionl chamber' withY air compressedfirom` said-duct-'forfcom- YbustionwithI fuel inl said chamber-, and -a turbine drivably connected to said l:con'iprerssorandv arwhich Arelatively little 'obstruction Vis voffered thereby to air '-flowing'through-said duct toesaid compressor, said means: being-lmovableifrom said :first Aposition 4forobstructing said air flow means responsive to acondition indicative cf f the l power output'ofsaid powerplant; and means controlled by said'responsivemeans for `moving said movvable-meansfromfisaid rstposition so as'ltoiobstruct saidlair "flow-'when saidy condition @gees beyond apredeterm-inedvalue-in a-pcwer increasing direction.r

2. In-combina'tlon'with an aircraftV gasturbine power v"plant lhaving a combustionichamber,` an annular forwardly fdl-rented: air intake'duct having' an annularlr inlet opening disposed adjacent 'to Vthefforwardend of-said power plant, van air compressor-for supplying said combustion chamber with air compressedlfrom :said ductiorfcombustion with'fuel inisaidrchamber,` and a-tu-rbine drivablyv vconnected' to `saidy compressor and 1 arranged to'be 'driven by combustion gas'csfrom said chamber; means v having --afiirst Aposition in which relatively little 'obstruction vis offered thereby yto air-flow lthrough Asaid fduct :to ysaid compressor, said means being movable from said v iirst position for obstructing said airflow;y means responsive to pressure within said =combustion chamber; and means controlled bysaid responsive `means -for moving said movable meansfrom said'rst position sor as toobstruct saidfairow when said vpressure vexceeds a predetermined value.

3.` In combination with van aircraft-gas turbine 'power plant' having a-fcor'nbustiony chamber', v a forwardly directed air intake duct, an':air-'co1npressorfor supplying said `combustionchamber with air compressed'from -saidductfor combus- "tion with fuel Vin said-chamber, -and-fa lturbine drivably connected to fsaid. compressor and-arranged to be "driven v byffcombustion 'gases'lfrom said chamber; -means 'having afirst position-in which 'relatively little obstructionv is offered thereby to Vair-flowthrough said `duct -to said compressor, saidmeans being movable from lsaid rst position or'obstructingsai'd airflow; 4means responsive '-.to "pressure 4within said combustion chamber; and means controlled by said .resp'onsiveimeanslfor moving said movable means from said Arst position so f as to' obstruct Vsaidzairflow to aniextent determined b'yithefextentt to Hwhich saidY pressure exceeds' a vpredetermined f Value.

4.: In combination with an'faircraft gas turbine `power` plant having"'a'-cembustion chamber, a vvforwardly directe'dLv air intake duct, lanfair compressorl for suppl-ying said vcombustion'.chamber Iwith air compressed from :said "duct v'for combus- -^tion-with fueliin sald's'chamber, and va turbine drivably'connectedto` saidcompressor and arranged -tofzbe-'drivemby combustion 'gases vfrom Vsaidchamber;'means having a iirst position Yin :which `relatively :little :obstruction 4 is offered *thereby* to "air-flow rIthrough'- said 'ductfto-*said compressor; saidmeans being movable from said vlirst'postion 'for obstructing said-"^`air-fiow means responsive to pressure Vwithin said combustion chamber; means v'controlled by f said responsive means for moving-saidlmovablemeansfrom said `Vfirst'position so as to obstruct-said air-liowwhen said pressure exceeds a predetermined value; and means for automatically decreasing said predetermined value with decrease of the temperature of the air entering said duct.

5. In combination with an aircraft gas turbine power plant having a combustion chamber, a forwardly directed air intake duct, an air compressor for supplying said combustion chamber with air compressed from said duct for comb-ustion with fuel in said chamber, an aircraft propeller, and a turbine drivably connected to said compressor and propeller and arranged. to be driven by combustion gases from said chamber; means having a first position in which relatively little obstruction is offered thereby to air-flow through said duct to said compressor, said means being movable from said first position for ob structing said air-flow; means responsive to pressure Within said combustion chamber; means controlled by said responsive means for moving said movable means from said first position so as to obstruct said air-flow when said pressure exceeds a predetermined value; and means for automatically decreasing said predetermined value with increase in the torque absorbed by said propeller.

6. In combination with an aircraft gas turbine power plant having a combustion chamber, an annular forwardly directed air intake duct disposed adjacent to the forward end of said power 3 plant, an air compressor for supplying said combustion chamber with air compressed from said duct for combustion with fuel in said chamber and a turbine drivably connected to said compressor and arranged to be driven by combustion gases from said chamber; means having a rst position in which relatively little obstruction is offered thereby to air-now through said duct to said compressor, said means being movable from y said rst position for obstructing said air-flow;

means responsive to pressure within said combustion chamber; means controlled by said pressure responsive means for moving said movable means from said first position so as to obstruct said air-now when said pressure exceeds a predetermined value; means responsive to the magnitude of a condition aiecting the power output of said power plant; and means controlled by said condition responsive means for decreasing said predetermined value of pressure when the magnitude of said condition changes a predetermined extent in a power increasing direction.

WILLIAM G. OVENS.

REFERENCES CITED The following references are of record in the lc of this patent:

UNITED STATES PATENTS Number Name Date 1,052,588 Janicki Feb. 11, 1913 2,225,310 Lindhagen et al. Dec. 17, 1940 2,447,696 Forsyth Aug. 24, 1948 

